Analysis And Numerical Simulation Of Rusting And Cracking Of Reinforced Concrete Beams Under Complex Working Conditions

The durability failure of reinforced concrete will cause huge losses.The corrosion of steel bar is the main reason for the durability failure of concrete.The most common and serious cause of reinforcement corrosion is chloride corrosion.When the chloride ion in the environment reaches the surface of the steel bar through the concrete cracks,it will react with the iron,produce rust products and continue to accumulate and expand,which will cause the cracking of the concrete protective layer.The cracking will also aggravate the erosion and erosion of chloride ions,resulting in a vicious cycle.Therefore,it is of great practical significance to study the rusting and cracking process of reinforced concrete under the erosion of chlorine salt.Based on the existing research results and numerical simulation method,the process of corrosion protection and expansion cracking of reinforced concrete after reinforcement corrosion is studied from different aspects.The main research contents are as follows:(1)the process of rusty expansion and cracking of reinforced concrete was simulated on the meso level.At the meso level,concrete is a non-uniform quasi brittle material composed of aggregate,mortar and interface transition zone between them.In order to show its meso characteristics,Monte Carlo method is used to generate random aggregate models by using MATLAB software,and the meso scale model of concrete is established by importing finite element software.Based on the brittle cracking model in ABAQUS software,the rusting and cracking process of reinforced concrete is simulated.The results show that the brittle fracture model can simulate the formation of real fracture diagrams,and visually show the occurrence and expansion of rust expansion cracks,which can reflect the cracking behavior of reinforced concrete more truly.In the evolution process of reinforced concrete expansion and cracking,the location of crack initiation is perpendicular to the maximum displacement loading direction.Cracks are generated first at the closest position to the interface layer and through the fragile interface layer around the aggregate,extending to the edge of the protective layer and finally penetrating the protective layer.(2)the corrosion cracking of reinforced concrete beams under the interaction of chlorine salt environment and static load is simulated on the macro level.Simulate the plastic damage model of concrete by using ABAQUS software.Using the temperature field to simulate the expansion force of steel bar expansion and synchronously apply static load,simulate the expansion process of reinforced concrete under the condition of static load and the coupling condition of the expansion force.It is concluded as follows: the damage caused by the coupling of static load and corrosion expansion force is far greater than the damage caused by the rust bulging load.Simple expansion caused by load damage is not large,but the damage caused by the coupling will increase sharply,which is consistent with the actual situation;the damage caused by static load coupling and expansion force in the steel side is more serious,reinforcement is easier to rust and rust cracks are easier to expand downwards.Corrosion expansion crack more easily extended down,transverse cracks are mainly concentrated in tension area which cause the cracking of concrete protection layer.The results are in agreement with the experimental results.(3)at the macroscopic level,the corrosion cracking of the reinforced concrete beams under the coupling of the chloride environment and the fatigue load is simulated.The simulation also uses the temperature load to simulate the rust expansion load,and simultaneously applies the fatigue load to simulate the rust and crack condition of the reinforced concrete beam under the condition of the coupling between the rust expansion load and the fatigue load.The simulation results show that the coupling damage is more serious in the middle part of the span,and there is a trend of spreading from the bottom to the middle,from the middle to the two sides.Due to the fatigue load,so the damage are generated more rapidly compared to the static coupling development,the damage of beam is more serious,after the initial damage,the whole beam will be completely damaged.coupling effect is also significant,compared with applying separate expansion load the damage caused by the coupling effect even more serious.Under two different conditions,the beam span reinforced concrete in ultimate damage were increased by 76% and 100% respectively,the simulation method can be used to simulate coupling fatigue,which has certain practical value.